Radiogoniometer



E. BELLlNl RADIOGONIOMETER May 22, 1928.

Filed Oct. 51, 12525 Patented May 22, 1928.

UNlTDi STAES ETTORE BELLINI, 0F PARIS, FRANCE.

RADIOGONIOMETER.

Application filed October 31, 1925, Serial No. 66,119, and in FranceNovember 20, 1924.

My invention relates to radio-goniometers employing fixed loops and oneof the objects of the invention is to provide a radio-goniometeremploying two fixed loops which may be tuned.

Another object of my invention is to provide a compact type ofradio-goniometers which may be used in aeroplanes.

Other objects and .advantages of my nvention will appear more fully ashereinafter set forth and as illustrated in the appended drawing.

Referring to the drawing, Fig. 1, 1s a diagrammatic sketch showing anaeroplane in the two wings of which the loops of the radio-goniometersare attached. Fig. 2, shows an arrangement, wherein the bridge circuitis tuned by means of a series of condensers.

F igs. 3, and 4, show arrangements wherein a bridge circuit may becoupled to toroidal inductances whereby the coils in the diametricallyopposed quadrants of the toroifdal windings further tend to diminish anyeffects of inequalities in the four condensers. Figure 5 is adiagrammatic representation ,of the uni-control arrangement of thetuning means.

In the old type of Bellini-Tosi receivingradio-goniometers similarperpendicular loops or coils connected in serles with a radio-goniometer(properly so called) were used;

The tuning of the two coils was effected the aid of variable condensersinserted in the middle of the above mentioned fixed and mechanicallyconnected coils. The two condensers evidently" were never identical, butthe degree of similarity obtainable was practically sufficient at theperiod when crystal detectors and damped waves were used.

Vith the adoption and introduction of continuous wave and vacuum-tubeamplifiers the situation changed entirely. The two more or less similarcondensers proved no longer adequate. The points or zero signal strengthdisappeared, while at minimum signal strength values the taking ofbearings became impossible owing to ob some and indistinct reception.The explanation for this situation is as follows:

In a continuous wave. system of radiocommunication, small differences inthe capacity. of. the two condensers were more than suflicient forproducing large differnces in the p ases of th strength. of the currentsin the two aerial s, which resulted in forming a revolving magneticfield inside the radio-goniometer. Therefore, no matter what theposition of the mobile coil may be, the zero position of signal strengthcould never be obtained. still more aggravated when using amplifiers bymeans of which the sensitivity of the circuits and their tendency tomagnify defects in reception existed. The remedies suggested to benefitthe above serious drawbacks were as follows:

First, to make the two tuning condensers independent of one another witha view to tuning the loops separately one after the other. i

Second, toadd a small equalizing condenser in parallel with that of thevariable condensers which showed the lowest capacity.

Neither of these two remedies proved satisfactory.

Aperiodic loops were next experimented with, that is, they wereconnected with the coils of the radio-goniometer without the insertionof condensers. This method gives good results for wave lengths above2,000 meters, while for shorter waves the loss of sensitivity is sogreat that in order to compensate for this loss it is necessary toprovide amplifiers which often comprise a great number of tubes.

Since the sensitivity of amplifiers made it possible to use smallrevolving loops or coils as radioqgoniometers interest in the problemdiminished considerably,to such a degree, was this the case that furtherinvestigation for the discovery of a solution of the above problemwasabandoned. However, in practice casesv are met with where the employmentof the two perpendicular loops is preferable to the use of one smallrevolving'coil. One of these cases is that of aeroplanes on which it isoften practically impossible to mount the small rotatable loops even ifit is only of a diameter of centimeters. As' a matter of fact, whenmounted inside the cockpit of the aeroplane they occupy very valuablespace. When placed on the outside'of the aeroplane, either above orbelow, they become a hindrance for navigation. An ideal solution to theproblem is found by disposing the two loops in such a manner that one isfastened on to one'of the wings of the aeroplane and the otheriscsituated in the cockpit'(see Fig.1), the

This inconvenience was two loops being connected with theradiogoniometer and an amplifier-detector.

The invention forming the subject matter of this application allowsofthe employmentof two perpendicular loops which are tuned to the wavelength to be received, vfor the purpose of being used as a rad io-goniometer.

To accomplish this end it is not necessary to use an individualcondenser for each loop, but rather a system of tour condensers,

1, 3, CllS- posed in a manner of a Whcatstone br dge as illustrated inFig. 2. The two loops are, connected. between AB and CD. The fourcondensers are connected mechanically ,by

means ofcompensatii'ig gearing, or by any other suitable mechanicalsystem, so that these condensers may be operated simultaneouslyindicated in Fig. 5 and at the same time to the zero or to the 180'degree posltlon. It can, be readily seen that the resultant capacity forthe coil connected at AB is:

T 1 t i 1 e c; ci e which reduces to f while that for the loop connectedbetween, CD will be:

1 v I 1 i ii j O1 O2 O4 03 which reducesito v v p 0 0 0 I- 0 0 0 -I 0 06 +C C C 7 1 2) 3 4) i The ratio between the two capacities is t O 1+02(Ga f (T) By the application of numerical examples it will be easytofind that this relationship comes invariably close to unity, providedthe tour condensers are not unduly different from another. The two coilswill be almost exactly tuned. The equation for this 'atio shows thatimviil be sufiicienttor the two I opposite condensers to be equal inorder tl'iat the resultant capacities may be alike.

Even if the capacities have thus been made practically alikeit 18 anadvantageous plan to make the resonance curves of the two loops as flatasfeasible.) In order to obtain 'this end it is necessary that the'twoloops should consist of only one turn, or else of several turnsinparallel, without any selfvinductance coil beingadded in'seriesexcept,

it must be und'erstoocL -the self-inductance coil to he added to thesmaller loop in order to make it equal to the-other one. a It may evenbe a good plan to provide shunts :tor the self-inductance of theseloops.

' :In this invention it isone of the objects not to provide two loopcondensers-that are absolutely alike, but merely to provide cons denserswhich diiler a little from one another, in order to ob'tain'withcontinuous wave and amplifiers the same results formerlyto be'realizedonly with crystal de-' teeter, and damped wave receiving apparatus.

With such a condenser arrangement it is possiblerto useradio-gonioi'neters"either-of the magnetic or of theelectrostatic type.

The arrangement comprising flou'r condensers may be further improved bythe use ota balanced circuit consisting of a toroid;

shaped winding, disposed in the manner in dicated'in Fig. 3, or betterstill as illustrated in Fig. at, and the uni-controlarrangement shown inFigure 5 may also besused' inconnection therewith. 'The magnetic actionsbetween the different parts of this winding tend to equalize thecurrents in the diametrically opposite quadrants thereby tendingjtofurther diminishthe' effects of inequalities between the fourcondensers.

Having thus described my invention, what" I claim is new and desire to'secureby Letters Patent is: f .l

1. Ina radio-gonionieter, a pair-of loop aerials and means for tuningsaid loop aeri als, said means consisting ofa bridge circuitcomprising"a'plurality of tuning ele ments formin the arms of saidbridge circuit, each 0? said loop aerials'being connected across apairofopposite terminals of the bridge. f 32. In a radio-gonionieter, apair ofloop aorials and means-for tunin'g said loop aerials, said meansconsisting of abridge circuit comprising a plurality of condensers Iforming the arms oi'fsaid bridge-c rcuit,

each Olf' said loop aerials beingconnccted pair of opposit'e terminalsof the brid'ge.- 1 c 3. In a radio-goniometer, a pair of loop aeria'ls,abridgecircuit having each pairg of oppositeterminalsconnected to theterminals of one of said loops, said bridge.

circuit comprising a plurality fofelements adapted to tune the loopaerials and means 'lior simultaneously-'ad]ust1ng the tuning eleoppositeterminals connected to the terminals of one of said loops, the arms ofsaid bridge circuit each comprising an inductance and a capacity fortuning the loops.

6. In a radio-goniometer, a pair of angularly disposed loop aerials, abridge circuit having each pair of opposite terminals connected to oneof said loops, and substantially equal tuning elements in the arms ofsaid bridge circuit simultaneously adjusted -for obtaining syntonybetween the loops.

7. In a radio-goniometer, the con'ibination with a pair of fixed loopaerials, of a bridge circuit having each pair of opposite terminalsconnected to one of said loops, and tuning elements in the arms of saidbridge circuit, each arm comprising a capacity con nccted symmetricallywith respect to an inductance.

S. In a radio-goniometer, two fixed loop aerials, a bridge circuitconnected thereto for tuning said loops, capacity means for balancingthe bridge circuit, additional means to further balance the bridgecircuit, said additional means consisting of a plurality ot'toroidal-shaped inductance coils, and means for connecting saidinductance coils to the bridge circuit.

9. In a radio-goniometer, the combination with two fixed loops locatedin planes atsubstantially right angles, of a bridge circuit associatedtherewith provided with a variable condenser in each of the bridge armsfor tuning the bridge circuit, said fixed loops being connected toconjugate ioints of said bridge circuit whereby syntony is effectedbetween the loops.

10. In a radio-goniometer, a loop aerial, asecond loop aerial arrangedat substantially right angles thereto, a bridge comprising four tuningelements, said loops being connected to conjugate points of the bridgecircuit, and simultaneously operated means for varying the impedance ofall said tuning elements.

' ETTORE BELLINI.

